An odd number less than five would have to be either 1 or 3, so this number has 2 possibilities.
The other number can be anything from 1 to 9, so there are 9 possibilities.
Total amount of possibilities: 2*9=18
Out of these 18 possibilities, the two that create a sum less than 5 are 1+4 and 3+2.
So the probability is 2/18=1/9